F. Kerckhof

Brucella ceti Infection in Harbor Porpoise (Phocoena phocoena)

We describe Brucella sp. infection and associated lesions in a harbor porpoise (Phocoena phocoena) found on the coast of Belgium. The infection was diagnosed by immunohistochemistry, transmission electron microscopy, and bacteriology, and the organism was identified as B. ceti. The infection’s location in the porpoise raises questions of abortion and zoonotic risks.

The Grey Seal (Halichoerus grypus) as a Predator of Harbour Porpoises (Phocoena phocoena)

In September 2011, two harbour porpoises (Phocoena phocoena) presenting extensive traumatic lesions washed ashore in Belgium. Similar lesions, with large parts of skin and blubber missing, had not been recorded before on harbour porpoises in Belgium but were recently observed in a number of cases in neighbouring countries. We compared the lesions with the mouth and teeth structure of possible predators. The circumstances of the strandings, the observations during the necropsies, and the results of seal skull investigations pointed towards seals, presumably grey seals (Halichoerus grypus), as the prime suspects for having caused the death of both harbour porpoises. Although purely aggressive behaviour cannot be completely excluded, predation is considered most likely as part of the skin and blubber tissue of the harbour porpoises was missing. The grey seal is an opportunistic predator, feeding on a variety of fish and cephalopods, and occasionally even on crustaceans and seabirds, but predation on harbour porpoises, or any other marine mammal, had to our knowledge never been described. This finding might shed a new light on the cause of death of some of the other mutilated harbour porpoises recently stranded on southern North Sea beaches, and it presents a case of a change in the feeding strategy of a top predator.

The barnacles Chirona (Striatobalanus) amaryllis (Darwin 1854) and Megabalanus coccopoma (Darwin 1854) (Crustacea, Cirripedia): two invasive species new to tropical West African waters

The collection of the barnacle Chirona (Striatobalanus) amaryllis (Darwin 1954) (Crustacea, Cirripedia) from the hull of a ship that had been operating for five months in the Gulf of Guinea and off Sierra Leone triggered a closer investigation of the cirriped fauna of the West African coast. Both C. amaryllis and Megabalanus coccopoma can now be added to the list of successful invasions in tropical West African waters. This discovery, as well as the circumstances of the findings, necessitates an update of the invertebrate faunal inventory of tropical West African marine waters.

Geographic patterns of biodiversity in European coastal marine benthos

Within the COST action EMBOS (European Marine Biodiversity Observatory System) the degree and variation of the diversity and densities of soft-bottom communities from the lower intertidal or the shallow subtidal was measured at 28 marine sites along the European coastline (Baltic, Atlantic, Mediterranean) using jointly agreed and harmonized protocols, tools and indicators. The hypothesis tested was that the diversity for all taxonomic groups would decrease with increasing latitude. The EMBOS system delivered accurate and comparable data on the diversity and densities of the soft sediment macrozoobenthic community over a large-scale gradient along the European coastline. In contrast to general biogeographic theory, species diversity showed no linear relationship with latitude, yet a bell-shaped relation was found. The diversity and densities of benthos were mostly positively correlated with environmental factors such as temperature, salinity, mud and organic matter content in sediment, or wave height, and related with location characteristics such as system type (lagoons, estuaries, open coast) or stratum (intertidal, subtidal). For some relationships, a maximum (e.g. temperature from 15–20°C; mud content of sediment around 40%) or bimodal curve (e.g. salinity) was found. In lagoons the densities were twice higher than in other locations, and at open coasts the diversity was much lower than in other locations. We conclude that latitudinal trends and regional differences in diversity and densities are strongly influenced by, i.e. merely the result of, particular sets and ranges of environmental factors and location characteristics specific to certain areas, such as the Baltic, with typical salinity clines (favouring insects) and the Mediterranean, with higher temperatures (favouring crustaceans). Therefore, eventual trends with latitude are primarily indirect and so can be overcome by local variation of environmental factors.

The role of physical variables in biodiversity patterns of intertidal macroalgae along European coasts

In the frame of the COST ACTION ‘EMBOS’ (Development and implementation of a pan-European Marine Biodiversity Observatory System), coverage of intertidal macroalgae was estimated at a range of marine stations along the European coastline (Subarctic, Baltic, Atlantic, Mediterranean). Based on these data, we tested whether patterns in macroalgal diversity and distribution along European intertidal rocky shores could be explained by a set of meteo-oceanographic variables. The variables considered were salinity, sea surface temperature, photosynthetically active radiation, significant wave height and tidal range and were compiled from three different sources: remote sensing, reanalysis technique and in situ measurement. These variables were parameterized to represent average conditions (mean values), variability (standard deviation) and extreme events (minimum and maximum values). The results obtained in this study contribute to reinforce the EMBOS network approach and highlight the necessity of considering meteo-oceanographic variables in long-term assessments. The broad spatial distribution of pilot sites has allowed identification of latitudinal and longitudinal gradients manifested through species composition, diversity and dominance structure of intertidal macroalgae. These patterns follow a latitudinal gradient mainly explained by sea surface temperature, but also by photosynthetically active radiation, salinity and tidal range. Additionally, a longitudinal gradient was also detected and could be linked to wave height.

Essence of the patterns of cover and richness of intertidal hard bottom communities: a pan-European study

Coastal ecosystems are highly complex and driven by multiple environmental factors. To date we lack scientific evidence for the relative contribution of natural and anthropogenic drivers for the majority of marine habitats in order to adequately assess the role of different stressors across the European seas. Such relationship can be investigated by analysing the correlation between environmental variables and biotic patterns in multivariate space and taking into account non-linearities. Within the framework of the EMBOS (European Marine Biodiversity Observatory System) programme, hard bottom intertidal communities were sampled in a standardized way across European seas. Links between key natural and anthropogenic drivers and hard bottom communities were analysed using Boosted Regression Trees modelling. The study identified strong interregional variability and showed that patterns of hard bottom macroalgal and invertebrate communities were primarily a function of tidal regime, nutrient loading and water temperature (anomalies). The strength and shape of functional form relationships varied widely however among types of organisms (understorey algae composing mostly filamentous species, canopy-forming algae or sessile invertebrates) and aggregated community variables (cover or richness). Tidal regime significantly modulated the effect of nutrient load on the cover and richness of understorey algae and sessile invertebrates. In contrast, hydroclimate was more important for canopy algae and temperature anomalies and hydroclimate separately or interactively contributed to the observed patterns. The analyses also suggested that climate-induced shifts in weather patterns may result in the loss of algal richness and thereby in the loss of functional diversity in European hard bottom intertidal areas.

Boccardia proboscidea and Boccardiella hamata (Polychaeta: Spionidae: Polydorinae), introduced mud worms new for the North Sea and Europe, respectively

There is a worldwide concern about the expansion of non-indigenous species because they may threaten local biodiversity as some of them may successfully outcompete native species. We report on the presence of two introduced mud worm species, Boccardia proboscidea and Boccardiella hamata , in the southern North Sea, where the former species has been discovered on groynes along the Belgian coast and both species were detected among Pacific oysters Crassostrea gigas in the south-western Dutch delta. Boccardia proboscidea is native to the North Pacific and was first detected in Europe along the Spanish Basque coast in 1996. Our record is the third for European waters and the first for the North Sea. Although B. proboscidea occurs in limited numbers and in ephemeral habitats along the Belgian coast, the species probably has established a permanent population, since it has been reported repeatedly after its first discovery in January 2011. Boccardiella hamata is native to the Atlantic and Gulf coasts of North America. This species has never been recorded from Europe before.Our research demonstrates that in under-studied habitats, such as man-made hard substrata, even well-established populations of newly introduced species may stay undetected. Due to a lack of monitoring of these particular habitats and insufficient knowledge about introduced biota, introduced species may pass unnoticed or may be overlooked for several years. A dedicated monitoring will be necessary to detect introduced species in an early stage. In view of the upcoming Marine Strategy Framework Directive requirements such monitoring will be inevitable.

Consistent patterns of spatial variability between NE Atlantic and Mediterranean rocky shores

Examining how variability in population abundance and distribution is allotted among different spatial scales can inform of processes that are likely to generate that variability. Results of studies dealing with scale issues in marine benthic communities suggest that variability is concentrated at small spatial scales (from tens of centimetres to few metres) and that spatial patterns of variation are consistent across ecosystems characterized by contrasting physical and biotic conditions, but this has not been formally tested. Here we quantified the variability in the distribution of intertidal rocky shore communities at a range of spatial scales, from tens of centimetres to thousands of kilometres, both in the NE Atlantic and the Mediterranean, and tested whether the observed patterns differed between the two basins. We focused on canopy-forming macroalgae and associated understorey assemblages in the low intertidal, and on the distribution of Patella limpets at mid intertidal levels. Our results highlight that patterns of spatial variation, at each scale investigated, were consistent between the Atlantic and the Mediterranean, suggesting that similar ecological processes operate in these regions. In contrast with former studies, variability in canopy cover, species richness and limpet abundance was equally distributed among spatial scales, possibly reflecting the fingerprint of multiple processes. Variability in community structure of low intertidal assemblages, instead, peaked at the largest scale, suggesting that oceanographic processes and climatic gradients may be important. We conclude that formal comparisons of variability across scales nested in contrasting systems are needed, before any generalization on patterns and processes can be made.

New extralimital record of a narwhal (**Monodon monoceros**) in Europe

On 27 April 2016, a dead narwhal (Monodon monoceros) was found on the bank of the River Scheldt, Belgium. It was the first record of this high Arctic cetacean in Belgium, and one of the most southerly records ever in Europe. Due to the decomposition of the carcass, the results of the autopsy remained inconclusive, but it is likely that the animal had died due to a long process of starvation. In the stomach, a large number of litter items were found which were probably ingested during the process of dying. We further provide information on the sighting of the live animal prior to the stranding and present an overview of the very few known records of narwhal in northwestern Europe.

First record of the North American amphipod Melita nitida Smith, 1873 in Polish coastal waters

Abstract The present paper reports the first observation of the North American amphipod Melita nitida Smith, 1873 in the Gulf of Gdańsk (the southern Baltic Sea, Poland). In 2014, 13 adult specimens, including 3 males, were collected in the Port of Gdynia, which is located in the western part of this waterbody.